Tag: Linux

Run fsck

On Linux systems, if a disk encounters a filesystem error, the physical drive may still be good but require a file system consistency check. Perform the following steps to attempt to correct this.

If the affected volume is a video storage volume:

1. Stop the ExacqVision server service. Open a Terminal window and enter:
   sudo service edvrserver stop<br><br>
2. Unmount the volume:
   sudo umount /mnt/edvr/X
   
   Replace the ‘X’ with your volume number.
   Example: If you have a write error on /mnt/edvr/2, you would enter:
   sudo umount /mnt/edvr/2
   
   NOTE: If this command fails, see Appendix below.<br><br>
3. Run fsck on this volume, again replacing ‘X’ with the volume number:
   sudo fsck -yv /mnt/edvr/X
   
   This command will tell the system to automatically attempt to fix any issues it encounters. This may take minutes or several hours depending on the number of filesystem errors and the size of the volume. When completed, the Terminal will return to a prompt awaiting a new command. <br><br>
4. When you have run fsck on all the affected storage volumes, reboot the system by entering:
   reboot
   
   OR
   
   Return to the Desktop and use the power icon to restart the machine. The drives will remount upon boot up.<br>br>

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Appendix

If drive fails to unmount, you will need to open the fstab file and comment out the mount point of the drive in question.
sudo gedit /etc/fstab

1. You will need to place a ‘#‘ character to the left of ‘Label=/mnt/edvr/X’
2. Save
3. Reboot the machine.
4. The drive that was commented out should not be mounted at this point.

Continue with step 3 above.
Reminder: Do not forget to re-edit the fstab after the fsck is finished and remove the # you added.

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What does fsck do?

The fsck command performs a consistency check and attempts to repair the filesystem from errors.

What causes filesystem errors?

When system processes or user activity require saving data or making changes to the filesystem, that data is first written to a buffer in memory (RAM). The system periodically moves the data waiting in the buffer to the hard disk. Therefore, at any moment, there is a difference between file changes waiting to be written to disk and what exists on the disks.

Filesystem errors and inconsistencies can develop due to hardware degradation, system halts, or unclean shutdowns. Sudden power loss and forced shutdowns occurring before the changes in the buffer are moved to permanent disk storage.

Components checked by fsck

Inodes
Inodes contain metadata about a file, which includes information like: whether the file is read/write or read-only, the type of file, the user ID of the file owner, file creation and modification date and time, and the number of bytes in the file.

Data Blocks
These contain the data that actually makes up the file.

Superblocks
The superblock contains details about the filesystem, such as the state of the filesystem, the filesystem size, the filesystem name and volume name(s), path name of the mount point, and number of inodes. Every change to the inodes also requires changes to the superblock.

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